DMARC stands for Domain-based Message Authentication, Reporting, and Conformance. It is an email authentication protocol that helps prevent email spoofing and phishing attacks. DMARC works by allowing domain owners to publish policies specifying how incoming email messages should be handled if they fail authentication checks.

Here's a breakdown of the key components and how DMARC works:

1. Authentication Mechanisms: DMARC builds upon two existing email authentication mechanisms: SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). SPF allows domain owners to define a list of authorized sending IP addresses for their domain, while DKIM enables the domain owner to digitally sign outgoing email messages.

2. DMARC Policy: The domain owner publishes a DMARC policy in their Domain Name System (DNS) records. This policy contains instructions for receiving email servers on how to handle emails that fail authentication checks. The policy can be set to three different modes: "none," "quarantine," or "reject."

• None: In this mode, the domain owner only monitors the email authentication results and receives reports but doesn't specify any action for failed messages.
• Quarantine: Emails that fail authentication checks are marked as potentially suspicious and may be placed in the recipient's spam or quarantine folder.
• Reject: Emails that fail authentication checks are rejected outright and not delivered to the recipient's inbox.

3. Email Authentication Checks: When an email server receives an email, it performs SPF and DKIM checks to verify the sender's identity. SPF checks if the IP address of the sending server is authorized to send emails on behalf of the domain. DKIM verifies the digital signature attached to the email using the domain's public key.

4. DMARC Alignment: DMARC verifies that the domain in the "From" header aligns with either the SPF or DKIM authentication results. This ensures that the visible "From" domain matches the authenticated domain.

5. DMARC Actions and Reporting: Based on the DMARC policy, the email server takes appropriate action when an email fails authentication. It can either mark the message, quarantine it, or reject it. Additionally, DMARC generates reports containing information about the authentication results, which the domain owner can analyze to identify unauthorized senders and potential abuse.

DMARC helps protect domain owners from email spoofing and phishing attacks by providing a framework for email authentication and enabling domain owners to define specific policies for handling suspicious or fraudulent emails. By implementing DMARC, organizations can enhance email deliverability, protect their brand reputation, and provide a safer email environment for their users.